“In particular, he (n.a.Fermat) is recognized for his discovery of an original method of finding the greatest and the smallest ordinates of curved lines, which is analogous to that of the then unknown differential calculus, and his research into number theory”

In today’s modern math, Archimede also did not produce much, even if for his time was a giant-genius.
Some people made positive comments about Riemann and Galois. These two along with Gauss, Euler, and Cauchy, are the mathematicians who have made revolution in mathematics.
Dare to imagine Number Theory without Riemann! Or complex function analysis, foundation of geometry, etc.
From Wiki:

”Riemann’s published works opened up research areas combining analysis with geometry. These would subsequently become major parts of the theories of Riemannian geometry, algebraic geometry, and complex manifold theory. The theory of Riemann surfaces was elaborated by Felix Klein and particularly Adolf Hurwitz. This area of mathematics is part of the foundation of topology, and is still being applied in novel ways to mathematical physics.
Riemann made major contributions to real analysis. He defined the Riemann integral by means of Riemann sums, developed a theory of trigonometric series that are not Fourier series—a first step in generalized function theory—and studied the Riemann–Liouville differintegral.
He made some famous contributions to modern analytic number theory. In a single short paper (the only one he published on the subject of number theory), he introduced the Riemann zeta function and established its importance for understanding the distribution of prime numbers. He made a series of conjectures about properties of the zeta function, one of which is the well-known Riemann hypothesis”
“Riemann’s idea was to introduce a collection of numbers at every point in space (i.e., a tensor) which would describe how much it was bent or curved. Riemann found that in four spatial dimensions, one needs a collection of ten numbers at each point to describe the properties of a manifold, no matter how distorted it is. This is the famous construction central to his geometry, known now as a Riemannian metric.”
“He was also the first to suggest using dimensions higher than merely three or four in order to describe physical reality[2]—an idea that was ultimately vindicated with Einstein’s contribution in the early 20th century.”
Imagine that he lived twenty more years! Dead at 40..what a world!

Niels Abel is on my next list.